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| Data Sheet No. PD94402 IRU1120 2A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR PRELIMINARY DATA SHEET FEATURES Stable with ceramic capacitor Guaranteed < 1.3V Dropout at Full Load Current Fast Transient Response 2% Voltage Reference Initial Accuracy Output Current Limiting Built-In Thermal Shutdown DESCRIPTION The IRU1120 is an adjustable linear voltage regulator. It is packaged in a 5-pin ultra thin-pak surface mount package. The adjustable output voltage can be set from 1.25V and up using a simple resistor divider. The input power can be supplied by a single 5V supply. The regulator is capable of supplying 2 Amps of continuous current with an input voltage of 5V. The output is protected by both current limit and thermal shutdown circuits. APPLICATIONS High Efficiency Linear Regulator Hard Disk Drivers, CD-ROMs, DVDs ADSL and Cable Modems TYPICAL APPLICATION 2.5V @ 2A VADJ 5 VOUT 4 R2 1K R1 1K C3 4.7uF X5R IRU1120 Gnd 3 VIN 2 VCTRL 1 5V 3.3V C1 4.7uF X5R C2 4.7uF X5R Figure 1 - Typical application of IRU1120. PACKAGE ORDER INFORMATION TA (C) 0 To 125 DEVICE IRU1120CP PACKAGE 5-Pin Ultra Thin-Pak TM (P) OUTPUT Adjustable Rev. 1.3 08/20/02 www.irf.com 1 IRU1120 ABSOLUTE MAXIMUM RATINGS Input Voltage (VIN) .................................................... Input Voltage (VCTRL) ................................................. Operating Junction Temperature Range ..................... Operating Ambient Temperature Range ..................... Storage Temperature Range ...................................... 10V 10V -40C To 150C -40C To 125C -65C To 150C PACKAGE INFORMATION 5-Pin Ultra Thin-Pak TM (P) FRONT VIEW 5 VADJ VOUT Gnd VIN VCTRL Tab is Gnd 4 3 2 1 uJA=308C/W for 1" Square Pad ELECTRICAL SPECIFICATIONS Unless otherwise specified, these specifications apply over CIN=CCTRL=COUT=4.7mF. Typical values refer to TJ=258C unless otherwise noted. IFL=2A. VADJ is connected to VOUT and VIN=VCTRL=5V unless otherwise noted. PARAMETER Output Voltage Line Regulation SYM VOUT RegLINE Load Regulation RegLOAD Dropout Voltage VDO1 Dropout Voltage VDO2 Dropout Voltage VDO3 Dropout Voltage VDO4 TEST CONDITION Io=10mA, TJ=258C Io=10mA, 08C< TJ<1258C Io=10mA, Vo+1.3V TYP 1.25 1.25 0.5 1.13 1.4 0.2 0.3 MAX 1.275 1.287 0.7 1.25 UNITS V %Vo %Vo 0.4 %Vo 0.48 0.6 0.63 V 0.75 0.94 0.9 V 1.1 1.27 1.05 1.2 1.25 V 1.2 V 2 Rev. 1.3 08/20/02 IRU1120 TEST CONDITION Note 2, Io=1.5A, VCTRL=VIN for the following: 08C< TJ<1258C -408C< TJ<1258C Dropout Voltage VDO6 Note 2, Io=2A, VCTRL=VIN for the following: 08C< TJ<1258C -408C< TJ<1258C Current Limit IOL DVO1=10% Below Regulation Minimum Load Current IO(min) Note 3, 5 Thermal Regulation RegTHERM Note 5, 30ms pulse, Io=IFL Ripple Rejection (Vcc to Output) PSRR Note 5, 100Hz PARAMETER Dropout Voltage SYM MIN TYP 1.2 1.3 1.35 1.44 3 1 0.1 32 0.5 0.3 0.003 1 MAX 1.35 UNITS V 1.5 4 5 V A mA %/W dB %Vo %Vo %Vo mA 2.3 3 Note 1: Low duty cycle pulse testing with Kelvin connections is required in order to maintain accurate data. Note 2: Dropout voltage is defined as the minimum differential voltage between VIN and VOUT required to maintain regulation at VOUT. It is measured when the output voltage drops 1% below its nominal value. Note 3: Minimum load current is defined as the minimum current required at the output in order for the output voltage to maintain regulation. Note 4: Temperature stability is the change in output from nominal over the operating temperature range. Note 5: Guaranteed by design, but not tested in production. PIN DESCRIPTIONS PIN # 1 PIN SYMBOL VCTRL PIN DESCRIPTION The control input pin of the regulator. This pin is connected to the 5V supply to provide base current for the pass transistor of the regulator. This allows the regulator to have very low dropout voltage, enabling use with low values of VIN. A 1mF high frequency capacitor is connected from this pin to VIN to ensure stability. The power input pin of the regulator. A minimum of input capacitance must be connected from this pin to ground to insure that the input voltage does not sag below the minimum dropout voltage during the load transient response. This pin must always be higher than the VOUT pin by the amount of dropout voltage (see data sheet) in order for the device to regulate properly. This pin is connected with ground. It is also the tab of the package. The output of the regulator. A minimum of output capacitance must be connected from this pin to ground to insure stability. A resistor divider from this pin to the VOUT pin and to ground sets the output voltage. See application section for divider setting recommendations and a circuit example. 2 VIN 3 4 5 Gnd VOUT VADJ Rev. 1.3 08/20/02 www.irf.com 3 IRU1120 BLOCK DIAGRAM VIN 2 VCTRL 1 4 VOUT + 5 VADJ CURRENT LIMIT THERMAL SHUTDOWN 1.25V + 3 Gnd Figure 2 - Simplified block diagram of the IRU1120. APPLICATION INFORMATION Introduction The IRU1120 adjustable regulator is a five-terminal device designed specifically to provide extremely low dropout voltages comparable to the PNP type without the disadvantage of the extra power dissipation due to the base current associated with PNP regulators. This is done by bringing out the control pin of the regulator that provides the base current to the power NPN and connecting it to a voltage that is grater than the voltage present at the VIN pin. This flexibility makes the IRU1120 ideal for applications where dual inputs are available such as a computer mother board with an ATX style power supply that provides 5V and 3.3V to the board. The IRU1120 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage, reducing the overall system cost with the need for fewer number of output capacitors. Output Voltage Setting The IRU1120 can be programmed to any voltage in the range of 1.25V to 5.5V by using two external resistors. The output voltage is defined as: VOUT = VREF3 1+ ( R1 R2 ) +IADJ3R1 Where: VREF = 1.25V Typically IADJ < 1mA Typically R1 and R2 as shown in Figure 3: VIN VIN VOUT VOUT IRU1120 VCTRL VCTRL Gnd Adj R1 IADJ = 1uA R2 Figure 3 - Typical application of the IRU1120 for programming the output voltage. The IRU1120 keeps a constant 1.25V between the adjust pin and the ground pin. By replacing a resistor (R2), between these two pins, a constant current flows through R1, subtracting the IADJ current out of the R1 to set the overall output voltage. Notice that since the IADJ is typically in the range of 1mA, it only adds a small error to the output voltage which is negligible. 4 www.irf.com Rev. 1.3 08/20/02 IRU1120 Thermal Protection When the junction temperature exceeds 1508C, the internal thermal protection shuts the IRU1120 down. Current Limit Protection The IRU1120 provides Over Current Protection when the output current exceeds typically 3A. The output decreases to limit the power dissipation. Stability The IRU1120 requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. A minimum input capacitance of 4.7mF and a minimum output capacitance 4.7mF Ceramic capacitor is needed for regulator stage as well as the specified minimum loads to guarantee stability. Transient Response and PSRR The input and output capacitors are critical in order to ensure good transient response and PSRR. The most important aspects of this are capacitor selection, placement and trace routing. Place each capacitor as close as physically possible to its corresponding regulator pin. Use wide traces for a low inductance path. Couple directly to the ground and power planes as possible. The use of low ESR capacitors is crucial to achieving good results. Larger capacitance and lower ESR will improve both PSRR and transient response. Thermal Design The IRU1120 incorporates an internal thermal shutdown that protects the device when the junction temperature exceeds the allowable maximum junction temperature. Although this device can operate with junction temperatures in the range of 1508C, it is recommended that the selected heat sink be chosen such that during maximum continuous load operation the junction temperature is kept below this number. The example below shows the steps in selecting the proper surface mount package. Assuming, the following conditions: VOUT = 2.7V VIN = 3.3V VCTRL = 5V IOUT = 1A (DC Avg) Calculate the maximum power dissipation using the following equation: ( IOUT)3(VCTRL - VOUT) 60 1 PD = 13(3.3 - 2.7)+( ) 3(5 - 2.7) = 0.63W 60 PD = IOUT3(VIN - VOUT)+ For Ultra Thin-Pak TM we have: RTHJA = 258C/W TA = 458C DT = PD3RTHJA = 0.63325 = 15.758C TJ = TA + DT = 60.758C Layout Consideration The IRU1120, like many other high-speed regulators, requires that the output capacitors be close to the device for stability. For power consideration, a ground plane pad of approximately one-inch square on the component side must be dedicated to the device where all Gnd pins are connected to dissipate the power. If a multilayer board is used, it is recommended that the inner layers of the board are also dedicated to the size of the pad for better thermal characteristics. Rev. 1.3 08/20/02 www.irf.com 5 IRU1120 TYPICAL CHARACTERISTICS IRU1120 Voltage Dropout Over Temperature 1.400 1.200 1.000 Volts 0.800 0.600 0.400 0.200 0.000 -40C -25C 0C 25C 50C 75C 100C 125C Vctrl=5V, VinDO @ 2A Vctrl=5V, VinDO @ 1.5A Vctrl=5V, VinDO @ 1A Figure 4 - Voltage dropout over temperature @ VCTRL=5V. IRU1120 Voltage Dropout over Temperature 1.500 1.400 1.300 1.200 1.100 1.000 0.900 Volts -40C -25C 0C 25C 50C 75C 100C 125C 150C Vin=Vctrl, 0.5A Vin=Vctrl, 2A Vin=Vctrl, 1.5A Vin=Vctrl, 1A Figure 5 - Voltage dropout over temperature @ VIN=VCTRL. IRU1120 Current Limit over Temperature 3.40 3.20 3.00 2.80 2.60 0 C 25 C 50 C 75 C 10 0 C 12 5 C 15 0 C -4 0 C -2 5 C Voltage I Limit @ 5V/5V I Limit @ 3.3V/5V Figure 6 - Current limit over temperature @ VCTRL=VIN=5V and VCTRL=5V and VIN=3.3V 6 www.irf.com Rev. 1.3 08/20/02 IRU1120 TEST DATA FOR IRU1120 1A 2A 0A 0A Figure 7- Load transient response @ IOUT 0 to 1A, VIN=VCTRL=5V, VOUT=2.5V, CIN=CCTRL=COUT=4.7mF, Ceramic. Ch1: VOUT (100mV/Div). Ch2: IOUT (0.5A/Div). Figure 8- Load Transient response @ IOUT 0 to 2A, VIN=VCTRL=5V, VOUT=2.5V, CIN=CCTRL=COUT=4.7mF, Ceramic. Ch1: VOUT (100mV/Div). Ch2: IOUT (1A/Div). Figure 9- Current Limit Characteristic, VIN=VCTRL=5V, VOUT=2.5V, CIN=CCTRL=COUT=4.7uF, Ceramic. Ch1: VOUT (2V/Div). Ch2: Shorted Current (IOUT) (1A/Div). IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 02/01 Rev. 1.3 08/20/02 www.irf.com 7 IRU1120 (P) Ultra Thin-PakTM 5-Pin A A1 K E U V B H M L P G D N C R C L SYMBOL A A1 B C D E G H K L M N P R U V MIN MAX 9.27 9.52 8.89 9.14 7.87 8.13 1.78 2.03 0.63 0.79 0.25 NOM 1.72 10.41 10.67 0.76 1.27 0.03 0.13 0.89 1.14 0.25 0.79 1.04 38 68 5.59 NOM 7.49 NOM NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS. 8 www.irf.com Rev. 1.3 08/20/02 IRU1120 PACKAGE SHIPMENT METHOD PKG DESIG P PACKAGE DESCRIPTION Ultra Thin-Pak TM PIN COUNT 5 PARTS PER TUBE 75 PARTS PER REEL 2500 T&R Orientation Fig A 1 1 1 Feed Direction Figure A IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 02/01 Rev. 1.3 08/20/02 www.irf.com 9 |
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